JPH0663002B2 - Sintering method of rare earth metal - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a sintered body of a transition metal powder containing a rare earth metal by a hot isostatic pressing (hereinafter abbreviated as HIP) method. Is.

[Prior Art] Recently, interest in magneto-optical recording has remarkably increased, and magneto-optical disks have been actively developed. In magneto-optical recording, recording is performed by applying light and a magnetic field to a magnetic material, and a magnetic thin film formed on the disk surface is used.

As a material of the magnetic thin film, transition metal-rare earth-based materials, for example, binary elements such as Fe-Gd and Fe-Tb, and three elements such as Fe-Co-Tb and Fe-Gd-Tb are considered promising.

The magneto-optical disk has the above-mentioned magnetic thin film material formed on the surface of a circular substrate such as synthetic resin by the PVD method.

As the PVD method, it is common to form a film by a sputtering device. This sputtering apparatus requires an alloy target having a composition substantially equal to that of the magnetic thin film, and the transition metal and rare earth metal in this target are deposited on the circular substrate.

The alloy target is divided into a casting target and a sintering target depending on its manufacturing method.

Conventionally, transition metal-rare earth alloys are extremely brittle, and it is difficult to make a large-area target suitable for mass production.The alloy once cast is made into powder, and the powder metallurgy method of forming and sintering is used. It was common to manufacture alloy targets. A hot pressing method is generally used as the powder metallurgy method, but the pressure is limited because it is manufactured by using a pressing die, and it is difficult to manufacture a dense target having a complicated shape.

In recent years, the HIP method, which has been used for the development of superhard materials and the like and has been attracting attention, performs high-temperature / high-pressure treatment using Ar gas or the like as a pressure medium.
A high pressure of 0 atm is obtained, and a large-sized and high-density target can be manufactured.

In the HIP method, an alloy powder obtained by crushing an ingot melted to a predetermined component or a powder of a base metal forming an alloy is filled in a capsule made of mild steel or stainless steel, and 10
^{After making} a high vacuum of ^-3 Torr or more and heating at 300 ° C or more to remove moisture and residual gas in the container, the container is sealed while maintaining the vacuum.

This container is put in a pressure medium such as high temperature and high pressure Ar gas to obtain a high density sintered body.

The target material thus obtained has a high density and a relatively high strength, but it is not preferable that the target material has a high oxygen content and, when used as a magnetic thin film material, deteriorates the magnetic properties.

[Problems to be solved by the invention]

Oxidation in the manufacturing process of the target by the sintering method includes oxidation in the process up to the powder and oxidation in the HIP process.

Of these oxidations, the present invention is intended to prevent oxidation during HIP treatment (in the conventional method, an increase in oxygen concentration of about 500 to 1000 ppm was observed).

[Means for solving problems]

In view of the above problems, the present invention prevents contamination of a sintered body by simultaneously putting a getter material in a container to be used during HIP processing. The place where the getter material is placed must be a spatially connected separate room to prevent mixing with the material to be sintered (see Fig. 1).

Further, the getter material that has entered this separate chamber needs to be sintered later than the body to be sintered, and therefore the strength of the separate chamber must be greater than the strength of the container. Specifically, in Fig. 1, a pad plate 2, which is much thicker than the container material 2,
3 is installed in the container 1, the bottom side pad plate 3 has a structure of two pieces, and the depression 7 is provided between the two pieces of the pad plate, and the ventilation path 6 connects the raw material powder.

As the getter material, a rare earth metal, Ti, Zr, or an alloy powder containing these as a main component is used. From the viewpoint of easy availability, iron-rare earth alloy powder or Ti powder is preferable. Further, the smaller the particle size of the getter material powder, the better the smaller the particle size.

[Operation] As the HIP process progresses, the container containing the material to be sintered is deformed by high temperature and high pressure. At this time, the space inside the container is filled with gas that could not be removed by vacuuming when the container was sealed and gas that was newly generated by high-temperature heating by HIP, and these are stronger than the container and deform. Is led to the slowest separate room and absorbed by the getter material.

[Example] Iron 96 was produced using a vacuum arc furnace having a molten tungsten electrode.
6 g, 118 g of cobalt, and 916 g of terium were melted to obtain 1950 g of Fe-Co-Tb alloy.

The vacuum arc furnace was replaced with high-purity Ar before melting. 99.99% electrolytic iron as the raw material metal, and 99.9% on the market
% Co, 99.8% Tb was used.

Crushing The above Fe-Co-Tb alloy was crushed in a stainless mortar under Ar atmosphere. After crushing, sieving is performed and particle size is 300-150
Classification was performed under μ, 150 to 100 μ, 100 to 45 μ, and 45 μ.

The results of analyzing these oxygen concentrations are shown in Table 1.

Molding Next, the alloy powder was sampled from each particle size, compounded as shown in Table 2, and filled as shown in FIGS. 1 and 2.
Also, the Ti powder as a getter material in Table 2 is 45
It is the one that has been screened under μ.

After filling the powder, the lid and the container were welded while flowing Ar from the evacuation pipe, then evacuated from the evacuation pipe, heated to 200 ° C. when depressurized to 3 × 10 ⁻⁴ Torr, and held for 5 hours. Then, it was sealed while maintaining a vacuum.

Sintering Put the above container in the HIP device and 100 ℃ × 1000kg / c
The temperature and pressure of m ² were maintained for 4 hours. After taking out the container from the HIP device and closing the can, a part of the obtained sintered body was analyzed. (See Table 3) Thereafter, the sintered body was used as a finish target plate in a plate of 101.6 ^mm x 5 ^t .

The sintered body was a dense one without pores, and defects such as cracks and cracks were not seen.

[Effect] From the results of the above experiment, it is understood that the target material of the container containing the getter material has almost no increase in oxygen concentration before and after the HIP treatment.

Further, this method can be applied not only to the transition metal-rare earth but also to the sintering of other easily oxidizable metals by HIP.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a loading method of the present invention, and FIG. 2 is a diagram illustrating a conventional loading method.

Claims (1)

[Claims] 1. A rare earth-containing metal sintering method in which a metal container is filled with metal powder and then sealed, and then the container is hot isostatically pressed at high temperature and high pressure, simultaneously with a sintered body, A separate room that is spatially connected to the material to be sintered is provided in the container, and the rare earth metal, Ti, Zr
Alternatively, a method for sintering a rare earth-containing metal, characterized in that a getter material made of an alloy powder containing these as a main component is added and hot isostatic pressing is performed.